The present invention relates to an improved process for converting crude oil fractions into an olefin product by hydrocracking the crude oil fractions to C.sub.2 - C.sub.5 paraffins and thermally cracking these to a C.sub.2 - C.sub.3 olefin mixture.
It is known from U.S. Pat. No. 3,598,724 that C.sub.3 - C.sub.4 paraffins can be produced from hydrocarbons boiling in the range from 100.degree.F. to 550.degree.F. by hydrocracking over a catalyst comprising mordenite mixed with a nickel/tin catalyst supported on an amorphous inorganic oxide.
Similar patents such as U.S. Pat. No. 3,385,782 suggest the hydrocracking of high boiling hydrocarbon fractions into C.sub.1 - C.sub.4 paraffins.
These prior art process, as well as U.S. Pat. No. 3,718,575, are primarily concerned with the production of LPG or liquified petroleum gas (C.sub.3 - C.sub.4) useful as fuels and thus were interested mainly in producing higher yields of C.sub.3 - C.sub.4 than the C.sub.1 - C.sub.2 yields.